Question: Simplify the following expression: $4\sqrt{18}$.
First, try to factor a perfect square out of the radical. $= 4\sqrt{18}$ $= 4\sqrt{9 \cdot 2}$ Separate the radical and simplify. $= 4\sqrt{9} \cdot \sqrt{2}$ $= 4 \cdot 3 \cdot \sqrt{2}$ $= 12\sqrt{2}$